Patent GB-307005-A (GB)
Title: Improvements in the manufacture of impregnated paper sacks
IPC: B31B1/74
Filed: 1928-06-12
Abstract: 307,005. Holter, A. March 1, 1928, [Convention date]. Materials, special, for bags.-Bags or sacks for hydraulic cements, fertilizers, &c. are manufactured from a number of webs of paper, one at least of which is waterproofed by treatment with water soluble substances, such as aluminium salts, and substances which react therewith, such as glue, soaps and lead acetate, the solutions being preferably applied separately to adjacent sides of two of the paper webs which are drawn from rolls and pass to folding and gluing apparatus. In manufacture, paper webs from rolls 11-15 pass under guide rollers 16-20 and then under and over rollers 21, 22 which feed the treated webs to gluing and folding apparatus. Pipes 23, 24 supply respectively solutions of soap and glue, and alum to adjacent sides of contiguous webs and, in the case of bags for hygroscopic or corrosive materials, a protective substance, such as molten paraffin, is supplied by pipes 25, 26. Instead of applying the waterproofing liquids separately, they may be mixed shortly before application. The Specification as open to inspection under Sect. 91 (3) (a) states also that paper sacks are rendered waterproof after manufacture by the application of impregnating-material to the sacks when closed, the interior surfaces being prevented from adhering during subsequent drying or hardening. Such impregnation is particularly advantageous when the sacks are made of several layers of paper or when they consist wholly or partially of substances other than paper. Percolation of the impregnating-liquid is prevented by the insertion of one or more layers of paper which may be in the form of a sack. Immersion may be effected by hand or by a belt conveyer, small openings in the sacks being held closed manually or by clips which may be part of the conveyer and opened and closed automatically. After impregnation, superfluous liquid is removed by rollers, brushes &c. and adhesion of the sides is prevented by splitting rollers or pins which open the sacks, these being carried by conveyers through drying chambers at 50‹ to 100‹ C. Impregnation of the exterior may be combined with an internal application, or several layers of previously impregnated paper may be used. As impregnating-material, aqueous solutions, tar and tar preparations, oil or molten paraffin may be employed. The process is particularly adapted for impregnating solutions which react to produce insoluble products, e.g., aqueous solutions of aluminium acetate, alum and glue, soap and alum, alum and lead acetate, or water-glass and sulphuric. or acetic acid, these being applied separately or in mixture. A preferred impregnating- liquid is a solution of glue and soap to which alum is added before use. Paper webs for the manufacture of sacks which are to have a final impregnation as set forth above, may be treated, as delivered from the paper making machine, with impregnating-solutions while still moist or, preferably, after removal of the major part of its moisture. The web 10, Fig. 1 (Cancelled), may pass through a vat 1 containing a first solution, over a first drying-roller 2, then through a vat 3 containing a second solution and finally over drying-rollers 4, 5, 6. The solutions separately applied may be glue or gelatine, alum, or lead acetate. Coagulation may be effected by substances in the paper. This subject-matter does not appear in the Specification as accepted.